A GaN high electron mobility transistor (HEMT) is a type of field effect transistor in which a heterojunction, rather than a doped region, provides the conductive channel of the transistor. In such a HEMT, the heterojunction (or the channel) exists in a contact region between two layers of semiconductor materials having different bandgaps. For example, in a gallium nitride (GaN)-based HEMT, a two-dimensional electron gas (2DEG) may be present within a contact region between a GaN substrate and a barrier layer (e.g., an aluminum GaN (AlGaN) layer). The 2DEG essentially is a concentration of electrons at the heterojunction that are free to move in two dimensions (i.e., along the heterojunction), but not in the third dimension (i.e., vertically through the device). Current associated with the 2DEG may flow between contacts positioned at spatially separated locations above the heterojunction. Although GaN-based HEMTs have been found to be particularly well suited for high power, high speed switching applications, GaN technologies do present some challenges to designers, when compared with more conventional semiconductor technologies (e.g., silicon-based technologies).